The present invention relates to a new and improved construction of apparatus for controlling the application of warp sections during warping operations, wherein there should be subjected to warping a winding of predetermined length of warp threads and application height from threads withdrawn in succession from the bobbins of a bobbin creel and each delivered through the agency of a stop motion and thread brake to a warping reed and at that location formed into a warp section upon the winding drum or reel of a warping machine.
In contrast to beam warping, during warping it is known to wind-up upon a warping drum or reel a number of warp sections next to one another, each composed of a multiplicity of threads or the like withdrawn from a bobbin creel. Thereafter, during beaming, these warp sections can be simultaneously wound onto a weaver's beam or back beam.
While heretofore for reasons of capacity, but also because of the increasing error- and disturbance sources, the maximum length of the warp ends or threads which are to be wound-up during the warping operation, the so-called warp length, was limited, at the present time it is desired to warp during a warping operation the greatest possible length of warp. Thereafter, such wound-up warp ends are wound onto a back beam in order to reduce the downtimes and manual operating times which result during each change-over operation both at the warping machine as well as also in the weaving mill at the loom, and thus, to obtain an increase in the production capacity or output.
Such capacity increase, as the same can be obtained by increasing the length of the warp which is to be subjected to the warping operation, of course requires not only appropriately wound bobbins for the bobbin creel, rather it also requires an increase of the winding diameter upon the winding drum an therefore the application height at such drum. The production of such bobbins is readily possible and the present day warping installations generally are completely capable of processing larger warp lengths, since as will be apparent from principles concerning surfaces or sheet-like areas, even relatively slight increase of the bobbin diameter and the application height, enables taking-up considerable increased length. The problems which hinder, or even prevent, increasing production in the described manner are attributable to disturbance factors which, with increasing application of the warp threads at the warping drum, quickly result in rendering impossible a correct beaming following the warping operation.
Such disturbance factors are, for instance, the different travel speeds of the warp ends or threads, attributable to the periphery or circumferential increase (as a general rule there is provided a correction device for maintaining constant the speed, but the correction increments or steps are too large); the increase of the thread tension due to the decrease of the bobbin diameter during progressive winding, resulting in increasingly harder winding and thus leading to reduced application, and the contamination or soiling of the warp threads or ends which occurs during winding and the start-up of the installation, and especially the thread brakes, which likewise cause an increase in thread tension and thus a reduction in the application of the warp sections.
Since the warp which has been beamed by the warping drum in each instance consists of a number of individual warp sections, the last-mentioned disturbance factors in particular result in a reduction of the bobbin diameter and contamination and heating of the installation, which notwithstanding the same setting of the warping machine, application of the first warp section does not correspond to that of the last warp section. In other words: the last warp section possesses a smaller application, leading to difficulties during subsequent beaming, when, as is the case during beaming, all of the warp sections are collectively simultaneously rewound. Since then the first warp section exhibits a greater application, thus also possesses a larger outer or external diameter than the last warp section with smaller outer diameter, then, when the difference exceeds a predetermined value, during beaming, for instance the last warp section is wound-up quite tautly, whereas the first warp section hangs-through loosely. Since after each revolution there is always wound-up more material at the first warp section than at the last warp section, it is possible in the presence of two great differences between both applications that there can no longer be wound-up any correct warp beam and the material subjected to the warping operation must be rejected.
The affect of the tension difference and equally that of the contamination of the installation can be neglected in the case of appreciably shorter warp thread lengths and smaller application heights derived therefrom, and accordingly, also smaller differences between the full bobbin and empty bobbin.
Further disturbance factors which heretofore opposed a desired increase in the length of the warp ends of threads which were to be exposed to the warping operation, also can be attributed to the thread material which is to be processed, especially during the processing of staple fibers. While it is possible when processing endless threads to wind such with existing installations into larger warp lengths due to the compactness and the lower frictional resistance thereof, during the warping of staple fibers owing to their more voluminous and aerated structure and, as a general rule, their larger diameter, there are present further obstructions. Not only does there result, with the same warp length, during warping of staple fibers, a considerably greater application than in the case of endless fiber material, but this greater application in conjunction with the properties of staple fibers has the result that such material reacts extremely markedly upon the heretofore mentioned disturbance factors.
In particular, the increase of the thread tension which arises in the creel owing to the decrease of the bobbin diameter, has particularly negative effects during warping of staple fibers, since during the winding of a thread warp section, it is desirable that the winding be harder at the inside, whereas at the outside the windings should be more loosely dispositioned. If, on the other hand, owing to increased thread tension the outer application is wound harder than the inner, then there occurs a pressing into the softer inner core, which can result in the warp end-application laterally sliding off and destroying the warp. Additionally, the winding or lap can float, with the result that the outer thread layers tend to rotate relative to the inner layers.
Also interruptions of the winding process, for instance for the insertion of divider cords or tapes into the wound warp sections for the purpose of subdividing the entire wound warp length or for repairing thread rupture or replacing depleted bobbins, can result in undesired differences in the application height of the finished winding or lap.